In the field of electronic parts and the like, anaerobic adhesives are often used in mutually fixing parts. This is due to the superior workability of anaerobic adhesive; that is, the anaerobic adhesive also has an ultraviolet ray (UV) curing property in most cases, and the adhesive is cured within a short period of time effected by the UV irradiation and anaerobic property.
However, when a coat having a low binding property with an anaerobic adhesive, such as Ni plating, is formed on an adherend, the adhesive may not be cured within a short period of time, which causes a problem in that peeling is liable to occur. Thus, it was necessary to apply a primer as a curing accelerator to the adhering face of an adherend having such a surface. An organic solvent mainly containing Cu ion, V ion and the like which accelerates the curing rate of the anaerobic adhesive is mainly used as the primer. It is a complex work to apply a primer to the whole adhering face of an adherend on which a coat having a low binding property with an anaerobic adhesive is formed, causing increase in costs.
In addition, when it is intended to adhere a layer on an adherend on which a coat having a low binding property with an anaerobic adhesive has been formed by using an anaerobic adhesive and without carrying out the primer application, it is possible to use a technique in which the adherend is fixed using a jig or the like in order to prevent its misregistration during the UV irradiation and then allowed to stand for a prolonged period of time, heated or the like. However, such a technique is more complex than the primer application and in the actual situation, this is not carried out in general.
Exceptionally, in the case where the adherend is a magnetized magnet and a ferromagnetic material such as silicon steel plate is used as the material to be laminated, by utilizing the magnetic force, the anaerobic adhesive may be cured by the UV irradiation for a short period of time without using a jig or the like. However, even in such a case, a positioning jig is generally used to prevent a misregistration of the magnet during the irradiation, because the magnetic force is not as strong as the adhesion strength in general. In this regard, when the jig is removed without confirming that the adhesive is sufficiently cured by the UV irradiation, an adhesion failure such as a misregistration of the magnet or a peeling of the adhesive occurs in some cases.
The R—Fe—B type permanent magnets (wherein R is at least one of rare-earth elements including Y) are rare-earth magnets which are inexpensive, rich in terms of resource and superior in magnetic properties in comparison with the conventional Sm—Co permanent magnets. However, since the R—Fe—B type permanent magnets themselves are easily oxidized, most of them are surface-treated with Ni plating, which is an inexpensive corrosion-proof coat having a good decorative property, a corrosion resistance, a chemical resistance and an abrasion resistance. A primer application must be carried out for them because of the poor reactivity of Ni plating with the anaerobic adhesives.
On the other hand, Cu and Fe are known as metals which have excellent reactivity and therefore do not require a primer. An R—Fe—B type permanent magnet comprising a Cu layer arranged on the surface has been known (e.g., see Reference 1). However, since the Cu layer is present on the surface as a film having a thickness of approximately from 1 to 60 μm, there is a possibility to cause a delamination. In addition, discoloration by the oxidation of Cu is significant, so that an after-treatment such as with, for example, a benzotriazole, indazole or imidazole nitrogen-containing cyclic compound must be carried out in order to prevent poor appearance, thus causing increase in costs.